Taggants for products and method of taggant identification

ABSTRACT

The tagging of articles is performed by applying microparticle taggants to the articles by means of a coating that adheres the particles to the surface of the articles. The microparticle taggants have a specific identifiable code or other quality. The coating material and microparticles are applied to the exterior surface of the articles and dried or cured thereon. The microparticles may have a magnetically attractive quality for purpose of collection of the particles for analysis. The microparticles are washed from the surface of the articles and collected in a vessel. The microparticles in the vessel are assembled or collected by means of a magnet.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of prior U.S. application Ser. Nos.09/997,485 and 60/334,462, both filed Nov. 30, 2001 and expresslyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to the application of taggants to productsand materials. The taggants may be applied to colored or treated seeds,other types of particulate, granular products, bulk materials or fluids.The present invention also relates to a method of collection of taggantsfor purposes of identification.

BACKGROUND OF THE INVENTION

Manufacturers and distributors of products often desire their productsto be identified within the distribution stream and after purchase. Theidentification information may include batch number, lot number, date ofmanufacture, method of manufacture, packing or shipment, etc. Anotherquality that may be desired to be identified is the authenticity of theproduct, so as to distinguish the product from unauthorized originals orcounterfeits.

The qualities and compositions of bulk materials, such as liquids,slurries particulate materials or granular products, are often difficultto mark. Such bulk materials may be marked with a chemical additive,microparticle or the like for purposes of later identification. However,substantial chemical or physical analysis is often required to identifythe taggant.

A variety of taggants and methods of taggant identification are knownfor marking bulk materials. For example, U.S. Pat. No. 4,053,433describes a method of marking substances with microparticles encodedwith an orderly sequence of visually distinguishable colored segmentsthat can be detected with a microscope or other magnifying device.

Another known taggant system is described in International PatentPublication No. WO 00/34937, filed by Tracking Technologies, Inc. Thispatent publication, which is herein incorporated by reference in itsentirety, describes a method of taggant identification using anassortment of colored elements, wherein each colored element representsa specific position in a binary number. A series of colored elements arecombined to represent a specific, identifiable binary number.

International Patent Publication No. WO 99/455 14, also filed byTracking Technologies, Inc. and which is also herein incorporated byreference in its entirety, describes a chemical tagging system whereinmultiple chemical additives are used to create a tracking number foridentification purposes.

Thus, existing tagging techniques include the use of microparticles,which are marked by chemical composition, color, shape, microscopicwriting, etc. The properties of these taggants may be varied toaccommodate the specific application. For example, particles may be madeof a magnetic or fluorescent materials to facilitate collection, of arefractory material to enhance particle survival in an explosion, ofchemically inert materials to enhance particle survival in a chemicalreaction, or of non-durable, soluble or reactive materials to enhancedispersal in fluids, aerosols or powder systems.

In a particular application, seeds that have been chemically orotherwise treated are required by law to be colored as a visibleindication of a chemical presence. Also, seeds that have beengenetically altered or engineered may be colored to serve as anidentifier of the genetic property. However, only a limited number ofcolors are available for such purpose and none are exclusive to specificproperties. Because the distributors of these seed products have createdsignificant value in their products, they are often able to chargehigher prices as compared to non-enhanced seeds. Color treatment alonemay, therefore, not be sufficient to identify the quality orauthenticity of the products. Also, a determination of the authenticityof the product may be required as a condition of sale. Therefore, thereis a need within the seed industry for a taggant and verification systemthat is easily and quickly applied. The attributes of such a system mayalso apply to other bulk materials, such as fertilizers, chemicals,paints, oils, plastics, pigments, clays, explosives, etc., and/orprepackaged materials, such as shampoo, conditioner, lotion, motor oils,pharmaceuticals or the like.

U.S. 2002-0129523-A1 (Hunt et al), WO99/455514 (Tracking Technologies);U.S. Pat. No. 4,606,927 (Jones); U.S. Pat. No. 4,053,433 (Lee et al); GB1568699 (3M) are incorporated herein by reference.

Known techniques for marking individual articles include use of anadhesive coating which binds the taggant to the article.

In bulk material such as explosives it has been known to disperseparticles with similarly sized bulk material and include ferromagneticmaterial in the taggant particles to permit isolation. This technique isnot particularly useful when particle sizes are very different, forinstance seed, feed particles and the like.

Seed identification problems can occur when seed is alleged to bedefective, if competitors sell unlicensed proprietary product asgenuine, or when a licensed grower uses crop from licensed seed as seedfor subsequent crops in contravention of the license. It would bedesirable to be able to identify seed by unique codes which would allowfor distinguishing genuine or licensed seed from competitive,counterfeit or saved crop seed.

Marking seeds with multilayer microparticles has challenges includingfixed quantity of adulterant material per seed unit, high cost, need formany codes to allow for batch code information as well as manufacturerinformation, etc.

SUMMARY OF THE INVENTION

The present invention relates to the tagging of articles, such asparticulate or granular type materials. The invention contemplates thata quantity of microparticles is applied to the articles or materials,with the microparticle taggant having a specific batch identifiable codeor quality. The microparticles are preferably applied to the articles bybeing mixed with a liquid coating material, which is applied to theexterior surface of the articles and dried or cured thereon. Thiscombination may be particularly applied to seeds which are normallycolor coated or include some other beneficial coating, such as apesticide and polymer. The tagging by means of the microparticles may beperformed to identify authenticity, origin, genetics, batch number, lotnumber, date of manufacture, method of manufacture, packing or shipmentor authenticity.

In one application, the microparticles at least in part have amagnetically attractive quality, i.e., are capable of being magneticallyattracted. The microparticles may also include a sequential color codingfor purposes of identification.

The present invention also relates to a method of tagging articles,material or the like. A quantity of microparticles is mixed with acoating that is to be applied to the material or articles. Themicroparticles have a coding system that relates to a specificidentifiable quality. In addition, the microparticles or a portionthereof may be capable of being magnetically attracted. The coating isdried or cured such that the microparticles adhere to the material orarticles.

A portion of the present invention further contemplates a method ofidentifying articles having microparticles adhered thereto by means of acoating material or the like. Again, the microparticles have a codingassociated therewith for purposes of identification. A sample of thearticles with the microparticles thereon is collected from a batch. Thesample is deposited in a collection vessel, preferably within a sieve orfilter, and then washed, typically by water or other fluid. The washingof the sample removes at least a portion of the microparticles adheredto the articles. The wash liquid is collected in the vessel and thewashed articles are removed from the vessel. The microparticles are thenassembled, the coding is read and the coding is correlated to theassociated quality. Assembly of the microparticles in the wash liquidmay be by any number of methods. One method contemplated is the use ofmagnetically attracted microparticles. A magnet can be used to help thesettling of the particles within the wash liquid. A magnetic probe mayalso be used to collect the microparticles for analysis.

Another aspect of the present invention is the provision of a kit forcollecting taggant microparticles that are capable of being magneticallyattracted. The kit includes a collection vessel and a sieve or filterfor holding and retaining a quantity of articles having taggantmicroparticles thereon. The openings in the sieve are sufficient topermit the microparticles to pass into the collection vessel during awashing operation. Means is positioned at or adjacent the base of thecollection vessel for creating a magnetic field to assist in thesettling of the microparticles within the wash liquid. A magnetic probefor collecting microparticles is also provided as part of the kit. Thekit further includes a collection surface on the magnetic end of theprobe. The collection surface is preferably removable from the probethat may be inserted under a microscope or the like for reading of thecode of the microparticles.

Other features and advantages of the present invention will beunderstood by those in the art on reference to the drawings anddescription herein.

The inventive system of releasing and collecting microparticles adheredto a bulk sample of articles substantially reduces the work andmagnification which would be required to observe the particles onindividual seeds and allows for taggant rates to be substantially lessthan one particle per seed.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there is shown in thedrawings various forms that are presently preferred; it beingunderstood, however, that this invention is not limited to the precisearrangements and constructions particularly shown.

FIG. 1 shows in cross section granular type articles having a coatingmaterial applied to the outside surface and a microparticle taggantadhered to one of the particles.

FIG. 2 shows one possible microparticle taggant for use as part of thepresent invention.

FIG. 3 shows a collection vessel as contemplated by the presentinvention for washing a sample of the tagged articles.

FIG. 4 shows the collection of microparticles by means of a magneticprobe.

FIGS. 5-9 are photographs of a test kit and its contents, illustrativeof a kit embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings, where like numerals identify the same or similarelements, there is shown in the figures an article which is generallyreferred to by the numeral 10. The article 10 may be any number ofproducts and of any size, but is shown herein as being granular in form.In one preferred application of the present invention, the article is aseed for producing crops, flowers, trees or the like. The granulararticle as illustrated has a coating thereon 12. On at least some of thearticles is a coded microparticle 14.

The coating 12 on the article 10 may take any form of polymer coating.As indicated one application of the present invention is the creation ofa taggant system for seeds. It is Federal Law in the United States thatany treated seed have a colorant added to prevent treated seed fromentering the food or feedstuff markets, which could lead to accidentalconsumption. Colorants, such as those manufactured and sold byBecker-Underwood, Inc. of Ames, Iowa, are thus used to identify theseeds treated with active ingredients such as fungicide or insecticide.Colors may also be used to segregate genetic technologies, such asherbicide resistance. Color coding can help eliminate confusion atplanting, and minimize potentially wrong chemical applications by thegrower. Colorants may also be used by seed companies to give theirproduct a distinctive look or brand identification. In addition tocolorants, polymer binders may be used to control dust-off duringtreatment/processing, planting, and rebagging.

Colorants are typically either dyes or pigments and maybe in stored dryor in liquid form. Colorants used for seed treatment applications can beorganic and inorganic. In preparing an application for the presentinvention, a combination of a pigment based liquid and polymer binderwas used. This material was found to provide sufficient binding for themicroparticles to the seeds without discoloration of the microparticles,which may prevent reading or create a false read of the associatedcoding.

Polymers were also used in preparing formulations for the seed taggantapplication. The polymer treatment of seeds is typically amacromolecular substance and can be inorganic or organic and stored indry or liquid form. Organic polymer types used in seed treatments arenatural, synthetic or semisynthetic. They also can be homo-polymers,block polymers and copolymers. Further, polymers can be water-soluble orwater insoluble. Polymers used in preparing seed taggants were acryliccopolymers, polyvinyl alcohol and salts of polymeric carboxylic acid.Again, each of these materials was found to create sufficient bindingeffect for the microparticles and to not cause harm to the subsequentreading of the associated coding.

It should be noted that the examples listed above are not limiting onthe types of coatings and polymers that may be used. Moreover, innon-seed applications a large variety of alternatives may be used.Coating formulas are often customized colorant and polymer solid-liquidsuspensions. In addition, various organic colorant and polymercombinations may be used without departing from the present invention.

In testing, microparticle taggant elements were combined withpolymercoatings at different concentrations from 0.05% to 1.8% byweight. It is preferred, although not required, that the taggants becombined with the polymer coatings before applying these products on theseeds or other articles.

In one working example, taggants were applied to corn seeds using aliquid polymer formulation prepared with 0.05% taggant elements. In thisworking example, 100 grams of seed treatment coating slurry was preparedusing 2.5 grams of a polymer binder formulation and 97.5 grams water.This seed treatment coating slurry was applied at the rate of 4 ml perpound of commercial hybrid corn seed. The corn seeds were coated in asix-quart stainless steel beaker and let dry. After the coated seedswere dried the seed samples were tested for the presence ofidentification taggants.

The taggant microparticles may take any form desired. The microparticlemust be capable of withstanding the application to the article by meansof a coating or the like, and also be capable of withstanding subsequentprocessing of the article.

In FIG. 2 there is illustrated an example of a microparticle taggant 14for use along with the present invention. As illustrated, themicroparticle is made in accordance with U.S. Pat. No. 4,053,433, thespecification of which is herein incorporated by reference in itsentirety. The microparticle 14 of FIG. 2 includes a color codingconsisting of a series of microscopic pieces of colored plastic filmsegments 16 fused together to form a rectangular “microsandwich”. Themicrosandwich as shown is a generally rectangular hexahedron having tencolor segments provided in sequence. However, any form or shape ofparticle may be used, as is discussed in the above-mentioned patent. Thecolor code may be read from left to right or right to left depending onthe specifics of the application.

Another form of colored microparticle may be made by applying a coloredresin to a hard, smooth substrate, such as glass. The colored resin istypically applied as a liquid, for example, by spraying onto thesubstrate or by spreading it out to a desired thickness using adraw-down bar. This type microparticle is describe in further detail inInternational Patent Publication No. WO 00/34937. In addition, thecoding sequence and character may be defined according to the disclosurein this International Patent Publication.

In FIG. 3 there is shown a collection vessel 18 for separating themicroparticles from the coated articles. The collection vessel 18includes a beaker or similar reservoir 20, a sieve or filter basket 22,and a base 24 having a series of magnets 26 positioned therein adjacentthe bottom of the beaker 20. During use, a sample of coated articles 10are placed in the sieve 22. A quantity of wash liquid, such as water, ispoured over the articles and agitated to cause a separation of themicroparticles from the articles. Other liquids or additives, such as asmall amount of detergent or other surface-active ingredient, may beused to assist in the release of the microparticles. The washing andagitation time may vary depending on the type of article, coating andwash liquid. Typically, the taggants are sufficiently displaced when asignificant amount of polymer coating is removed from the articles andis in solution in the wash liquid.

In the application of microparticles having a magnetically attractivequality, a magnetic field is created at the base 26 of the beaker 20 bymeans of permanent magnets 26. The position, number, size and strengthof the magnets may vary. In addition, it is contemplated that a magneticfield can be created by electric means, if desired. The magnetic fieldhelps to settle the microparticles, which because of their size andmaterials may desire to remain in suspension and/or be easily disturbedwithin the wash liquid.

As illustrated in FIG. 4, the microparticles 14 within the wash liquid28 are collected by means of a collection probe or wand 30. The wand 30has a magnet 32 on one end for attracting the microparticles 14. Acollection surface 34 is wrapped around the magnetic end 32 of the wand30. The collection surface 34 may be paper, filter paper or the like andis used to support and retain the collected microparticles for purposesof identification. A retainer ring 36 secures the collection surface 32on the end of the wand 30. After collection of the microparticles, thewand 30 is removed from the wash liquid 28. The retainer ring 36 is thenremoved, permitting the separation of the collection surface 32. Thesurface 32 can then be placed under a microscope or the like (see FIG.8) for analysis of the coding on the microparticles.

The method of separating and collecting the taggants is contemplated tobe performed easily and quickly. Thus, a sample of articles, such asseeds, can be analyzed prior to purchase to determine the age, qualityor authenticity of the products. Moreover, the simplicity of thecombined elements for analysis lends itself to assembly in a kit thatcan be sold or provided separately from the bulk materials. Prior topurchase of the bulk materials, or prior to taking delivery, the kit canbe opened and the articles tested. Assuming conformance to thepredetermined or authenticated code, the bulk material purchase can becompleted with reasonable certainty of the desired qualities of theproduct.

In preferred embodiments, a binder, suitably the polymer, binds thetaggant to the seed so that it stays on the seed during handling, andthen the wash liquid releases the taggant from the binder so that it canbe collected from a sample of the seed. The wash liquid may release thetaggant by degradation of the polymer coating or dissolution.

As an alternative to the multiple side magnets depicted in the FIG. 2, asingle central magnet embedded in the base 24 may be used. The wandmagnet is preferably stronger than the base magnet so that it cancollect particles from the bottom where the base magnet has concentratedthem. Because of this wash/concentration system it is not necessary thatevery seed have an associated taggant particle or even that everyparticle carry the full code. It is only necessary that the volume ofseeds washed be sufficient to provide enough taggant particles to thebeaker that all relevant particles can be seen when concentrated andcollected in this manner.

FIGS. 5-9 are photographs of a test kit and its contents illustrative ofa kit embodiment of the present invention.

FIG. 5 shows a field test kit microscope on the left; base surfaces,beaker and collector/sieve in the center; and a magnet tipped collectionwand, extra batteries and filters on the right.

FIG. 6 shows a beaker base with magnet for taggant concentration.

FIG. 7 shows a collector/sieve. A fixed volume of seed can be collectedthen put into beaker which is filled with wash solvent after appropriateperiod the collector/sieve is removed with the seeds. The taggantparticles remain behind in the beaker with the wash solvent.

FIG. 8 shows a full kit assembly showing beaker base with beaker, sieveon the side, microscope with light, extra filters, wand, beaker,collector/sieve, batteries for microscope light.

FIG. 9 shows a magnetic nut on the end of the wand which allows forcollection of the concentrated taggant. Filter papers go over the nut sotaggants collect on a visible surface which can be removed and examinedunder the microscope.

On the following pages 10-26, matter incorporated from prior applicationSer. No. 09/997,485, published as U.S. 20020129523-A1, is provided tofurther assist in understanding the coding systems which are aspects ofthe present invention.

Suitably, the marker layers each comprise a distinguishably differentcolor or color enhancer. In some embodiments, each of the specificmarker layer combinations employed in the taggant has the same number oflayers and/or each specific marker layer combination employs two orthree layers. The taggant may be formulated with a binder, such as anadhesive or coating compositon, which fixes the taggant to the object ormaterial.

In some embodiments of the invention, each said specific marker layercombination employs two layers, the numeric code is a binary code havinga predetermined number of places and having two values at each place,each microparticle set codes for one said value in a specific place inthe code and the absence of said microparticle set in the taggant codesfor the other said value at said specific place.

In a further aspect of the invention, the microparticle sets employed inthe taggant include at least one datum marker layer, which function toidentify an orientation of the value marker layers coded and is alsocoded to include place information, and at least two value marker layerscoded to specify a value within the place, the datum marker layer(s)being readily distinguishable from the value marker layers.

To mark an individual object, the series of microparticles are typicallyadhered to the object.

Preferably, each microparticle comprises at least two distinguishablecolors. In some embodiments, each microparticle comprises no more thantwo distinguishable colors.

Methods are known for manufacturing microparticles, for example asdisclosed in U.S. Pat. No. 4,053,433. Another method for manufacturingmicroparticles includes applying a colored resin, such as Resimene® 735,to a hard, smooth substrate, such as glass. The colored resin istypically applied as a liquid, for example, by spraying the liquid resinonto the substrate or by applying the liquid resin to the substrate andspreading it out to a desired thickness using a draw-down bar. After thefirst coating has dried, a second coating is applied over the firstcoating using a resin of a second color. After the second coating isdried, the resin is cured. Typically, the coated substrate is heated toapproximately 350° F. for about 30 minutes to cure the resin. After thesubstrate and resin are cooled, the coating can be scraped from thesubstrate, for example, using a razor blade. The microparticles may thenbe ground and sieved to collect the desired sized particles.

The size of the microparticles can vary, depending on the object beingidentified. In some instances it might make sense to identify an object,for example particulate material such as fertilizer or liquid materialsuch as shampoo, with microparticles that are about 10 microns to about500 microns at their average cross section dimension. In contrast, itmight make sense to identify a large object, such as an automobile,using microparticles that are about 0.5 millimeter to about 1 millimeterat their average cross section dimension. For other uses, particles thatare greater than 1 millimeter at their average cross section dimensionmight be suitable, for example, to mark large particulate matter such asmulch. For many applications, microparticles that are small enough topass through a 50-100 mesh screen are suitable. Typically, themicroparticles are about 10 microns to about 500 microns at theiraverage cross section dimension, more typically about 50 microns toabout 500 microns, most typically about 50 microns to about 100micrometers. For some applications even smaller dimensions may beemployed, for instance about 0.1 microns to 10 microns.

The concentration of microparticles used to identify an object can alsovary. For example, when the microparticles are used to identify aflowable material, the microparticles might be incorporated into thematerial at a concentration of 0.0001 to 1 part by weight for every 100parts by weight material. If the microparticles are used to identify anindividual object, the microparticles may be combined with an adhesiveat a concentration of 0.0001 to 1 part by weight for every 100 parts byweight adhesive and applied to the individual object for identificationpurposes. Preferably, the adhesive is transparent, such that themicroparticles are readily visible. Examples of suitable adhesivesinclude lacquers and enamels, such as acrylic, alkyds, etc.

The disclosure provides a system for marking an object, for example, toindicate ownership, source or origin. The method involves the use of anassortment of microparticles that are used as a part of a coding systemwherein each microparticle represents a specific place in a number. Aseries of microparticles can be combined to represent a number and usedto mark an object. The number may be dictated from outside themicroparticle system since there are no gaps in the numeric sequence.

To facilitate an understanding of the method, a brief discussion of anumeric system will first be provided.

In the decimal system, numbers are organized into numeric positions or“places.” For example, a “hundreds” place, a “tens” place, and a “ones”place such that the number “193” is 1-hundreds plus 9-tens plus 3-ones.According to this system, the “ones” place means 10⁰, the tens placemeans 10¹, and the hundreds place means 10². The decimal system uses thedigits 0-9 to represent numbers. To represent a larger number, such asthe number twelve, multiple places are used.

The binary system works under the same principles as the decimal system,only it operates in base 2 rather than base 10. In other words, insteadof the places being 10², 10¹, and 10⁰, they are 2², 2¹, and 2⁰. Insteadof using the digits 0-9, only the digits 0 and 1 are used. A numberlarger than 1, for example the number 3, is represented using multipleplaces. The decimal number 3 is represented by the number “11” in binary(1×2¹)+(1×2⁰).

The coding system may involve an assortment of microparticles in whicheach microparticle represents a specific place in a binary number, suchthat a series of microparticles can be combined to represent a number.In a binary system, for example, the standard may be established suchthat when a particle is present in a mixture, the numeric placerepresented by that particle contains the value “1”. If a particlecorresponding to a particular numeric place is not present in a mixture,the numeric place represented by the particle contains the value “0”.Alternately, in a numeric system established for base 3, a standard maybe established where the absence of a particle is represented by thevalue “0” at that place, the presence of a specific form of the particle(designated, for example, by color, presence or absence of a visualenhancer, shape or number of layers) represents the value “1” at thatplace, and a different form of the particle represents the value “2” atthat place, and so on.

Each microparticle can include a single color, or a plurality of colors.Preferably, each microparticle comprises at least two distinguishablecolors. In one embodiment each microparticle comprises just twodistinguishable colors.

If single microparticles are made using eight different colors, 2 ⁸ or256 binary numbers can be created. If the same eight colors are used tomake dual-color microparticles (i.e., particles having two color layerseach), 28 unique dual-color microparticles can be created (see Table 1,below). The 28 unique microparticles can be used to formulate 2²⁸, or268 million binary numbers. TABLE 1 gold silver Magenta black greenyellow blue Total 1 red x x x x x x x 7 2 blue x x x x x x 6 3 yellow xx x x x 5 4 green x x x x 4 5 black x x x 3 6 magenta x x 2 7 silver x 18 gold 0 28

Note that at this juncture, the numbering system makes a distinctivedeparture from the prior art of microparticle taggants. The eight colorsare no longer used to represent numeric values. Instead they are used tocreate a set of color combinations that is greater in number than theoriginal eight colors and the resulting combinations are then used torepresent numeric information. Values are assigned only to thosecombinations that are permissible in a layered taggant, so that no gapsoccur in the numeric sequence. As shown in Table 1, pairing eight colorscan create twenty-eight distinctive color combinations representingnumeric information.

The number of microparticles possible, X, is characterized by theequation:X=1+2+3 . . . +Nwhere N=K−1 and K=the number of colors available.

For example, if six colors are used, N=1+2+3+4+5=15, and so 15 pairedcolor microparticles can be made which can formulate 2¹⁵, or 32,768binary numbers.

If four colors are used, for example, blue, red, yellow and black,permutations of the four colors can create six distinctivemicroparticles: blue/red, blue/yellow, blue/black, red/yellow, red/blackand yellow/black. According to the system of the invention, each of themicroparticles (in this example, six dual microparticles) is assigned torepresent a specific place in a binary number. A representative systemis shown in Table 2 below. For purposes of this example, the standard isestablished in Table 2 that place #1 represents 2⁰, place #2 represents2¹, place #3 represents 2², and so on. TABLE 2 Colored Particle BinaryPlace blue/red place #1 blue/yellow place #2 blue/black place #3red/yellow place #4 red/black place #5 yellow/black place #6

If, for example, three different codes are needed to mark three objects,the binary numbers 10100, 111100 and 101000 may be the binary numbersassigned to each of the items. Using the representative system shown inTable 2, above, the particle representation of the first binary number,10100 is formulated using the particles that represent the fifth andthird binary places (i.e., red/black and blue/black). An appropriatequantity of each of the red/black particles and the blue/black particlesis thus combined. To formulate the particle representation of the binarynumber 111100, the particles representing the sixth, fifth, fourth, andthird binary numeric places are combined. For the binary number 101000,the particles representing the sixth and fourth binary places arecombined. Once the object is marked, identification of the object can bemade by examining the series of microparticles.

Advantageously, quantitative information about the microparticles is notneeded to identify the object. The presence or absence of specificmicroparticles need only be detected. Thus, the method is lessvulnerable to problems caused by dilution and/or contamination of thematerial.

Additionally, the method allows for the formulation of a large set ofunique microparticles, particularly microparticles that are each made upof more than one color (e.g., “multi-colored” particles). Multicolorparticles require fewer colors to provide a larger number of distinctivemicroparticles. Multicolor microparticles are advantageous in thatfinding, for example, 28 distinctive colors may be difficult because ofthe limited number of colors to chose from. For example, rather thanusing permutations of eight colors to form 28 unique tags (as describedabove), 28 different colors would have to be used. To acquire 28different colors, one might consider using gold, bronze, and copper.However, these colors may be difficult to differentiate from oneanother, particularly when admixed with other materials. Because gold,bronze and copper colors are not very distinctive from one another, useof these three colors in a system could result in errors in productidentification. Thus, only one color from this group, such as gold, maybe a practical choice.

In some embodiments of the invention, particles having two coloredlayers are preferred. Dual layer microparticles provide a greatdiversity of combinations while reducing the impact of byproducts. Forexample, during manufacturing, shipping, handling or other processing,dual layer microparticles may fracture to form single color byproducts.Because the relative size of the single colored byproduct is about 50%of the overall thickness of a dual layer microparticle, the singlecolored product is easily removed from the microparticles during ascreening phase of production. Additionally, single colored byproductremaining during product identification is not easily confused with adual layer microparticle. Thus, if a single color particle, such as asolely green particle, is visible in a marked material, it can bediscounted; and only paired colors, such as green/silver andgreen/yellow are considered as valid.

In contrast, a 5-layered particle can fracture to form 4, 3, 2 and1-layered byproducts. However, 4 and 3-layered byproducts may be tooclose in size to the 5 layered particles to be effectively removed byscreening during the manufacturing process (for example, a 4 layeredbyproduct is about 80% of the thickness of a 5 layered microparticle).Identifying 5-layered particles among 4 layered byproduct particles maymake product identification more difficult. The likelihood of having a3-layered byproduct reduces effective use of 3-layered particles incombination with 5-layered particles. Additionally, when particles areused having more than two color layers, an indicator may be necessary todenote which side of the particle represents the highest or lowest valuenumeric place.

According to the invention, a specific series of microparticles is usedto mark an object. As used herein, the term “object” includes both solidand flowable materials. As used herein the term “flowable” refers to anymaterial or substance that changes shape or direction uniformly inresponse to an external force imposed on it. The term applies to bothliquids (such as oils and shampoos) and particulate matter (such asfertilizer, sand and clays). It should be noted that liquids can varygreatly in viscosity and may contain suspended particulate matter.Particulate matter can vary greatly in size and includes within itsscope, fine particles with an average diameter of less than about 5 mm,and large particles with an average diameter greater than about 5 mm.Examples of flowable materials include, but are not limited to,petroleum products; personal care products such as shampoo, conditioner,lotion, cologne and perfume; pharmaceuticals, etc. The series ofmicroparticles can be combined with a flowable material, (prepackaged orbulk) or adhered to an individual object for identification.

The microparticles may be incorporated into the material at aconcentration of 0.00001 to 1 part by weight for every 100 parts byweight material. Much lower concentrations, for instance one part perten billion by weight, or even less, can be used when suitableconcentration and isolation methods are employed, such as agneticconcentration and isolation of microparticles attractive to magnets.

If the microparticles are used to mark an individual product unit, themicroparticles can be combined with a binder, for instance an adhesiveor coating formulation, preferably a transparent binder. Suitable bindermaterials are known and include lacquers and enamels such as acrylicsand alkyds, hot melts, etc. The resulting particle/adhesive mixture canthen be applied to the surface of an individual object foridentification purposes. It should be noted that some flowable products,such as shampoos, conditioners, and lotions are often packaged. In thecase of a prepackaged material, the microparticles can be combined withthe packaged material, or adhered to the container or bottle, label, lidor any other packaging or shipping container.

The marked object can be subsequently identified to determine thepresence or absence of microparticles. If the particles are visible tothe naked eye, the examination may be performed without additionalequipment. For particles that are not easily visualized by the nakedeye, equipment such as a light microscope or a magnifying glass may beused. Typically, the microparticles can be examined using a common 40and/or 100 power inspection microscope.

The presence or absence of specific microparticles is detected andrecorded and a standard, such as that shown in Table 2, is consulted todetermine which place in a binary number the particles represent. Afterdetermining which particles represent which binary numeric places, thespecific binary number can be determined. An individual can perform thedetection and analysis manually. Alternately, it is foreseen that thesystem can be automated such that a computer performs the detection andanalysis. If desired, the microparticles can be separated from theobject before examination. For example, a premium grade personal careproduct, such as a shampoo, conditioner, or lotion, marked with a seriesof microparticles can be filtered to remove the particles. The particlescan then be washed dried and viewed under a microscope. Personal careproducts are often marked for the purpose of identifying diverters ofthe distribution chain. Using shampoo as an example, the microparticlesmay be applied to the product itself, the bottle, the label, the cap, orother packaging or shipping containers.

The end user can prepare the microparticles, or the microparticles canbe “pre-manufactured”, placed in appropriate storage containers andsupplied to an end user as a kit. In some embodiments, the kit couldinclude a code key identifying the place (and value, if applicable) in anumber represented by each of the microparticles. The kit may evencontain an adhesive for applying the microparticles to an object. Theend user may also formulate codes from an inventory of pre-manufacturedmicroparticle sets at the time of use.

If desired, the particles may also include visual enhancers. Visualenhancers include, for example, pearlescent colorant, metal flakepigments, or glass microspheres, glitter etc. Visual enhancers providethe particle layers with a higher localized reflectance and a morecharacteristic appearance. Thus, the colored layers of the particles aremore easily distinguished from each other, the substrate, and/or themarked material. For example, if green layers are used on a greensubstrate, visual identification could be difficult because the greenlayers might be “camouflaged” by the green background.

A visual enhancer may also be added to denote a numeric value to themicroparticle. For example, a standard could be established that theabsence of a colored chip denotes the value “0” for a specified place,the presence of a colored chip without enhancer denotes the value “1”for the same place, and the presence of a colored chip with a visualenhancer denotes the value “2” for the place.

The addition of visual enhancers can also be used to furtherdifferentiate color layers of the particles from one another. Forexample, primary colors (i.e., red, yellow and blue) are easy todistinguish from one another. However, it may be more difficult todistinguish primary colors from secondary colors (i.e., orange, green,and purple). Thus, if primary colors are used in combination withsecondary colors, the thin colored layers of the microparticles may beless distinctive.

To reduce the possibility of confusion, a visual enhancer can be addedto either some or all of the colors. For example, the secondary colorsmay include a glitter visual enhancer so that glitter-orange is lesslikely to be confused with (non-glitter) red or (non-glitter) yellow.

As an alternative to visually distinguishable characteristics such ascolor and visual enhancer features, the layers of the inventivemicroparticle systems may be distinguished by machine-readablecharacteristics. Machine-readable characteristics may include color orcolor enhancer characteristics difficult to distinguish visually; IR orUV absorption, reflection, fluorescence or transmission characteristics;magnetic; and/or radioactive characteristics.

Higher Numeric-Base Multiparticle Taggant Systems

If the base of the numbering system is too low, the number of particlesrequired for a given numeric code may be impractical for manyapplications, thus not being suitable for many customer needs. Forexample, using a binary, or base 2 system, anywhere from 1 to 20particles are needed to count to 1 million in decimal, and the number ofparticles changes from code to code. Thus, while dual layer particlesprovide many advantages, their use in the inventive system does havesome disadvantages. In particular, the amount of microparticle materialneeded to identify a single number is widely variable, depending on theparticular number coded. For instance, an adhesive or coatingformulation desirably will be formulated with a specific concentrationof each different particle per unit volume or weight of the formulation,the concentration being selected to be high enough such that thedetection method selected for identifying the code will essentiallyalways find at least one, and preferably more than one, of each distinctparticle used in the coded number. However, for a 28 pair code system,as discussed above, the number of particles employed in a coded numbercan vary from 1 to 28. Thus the volume or weight amount of taggant,which the adhesive or coating formulation would need to accommodate,will vary by a multiple of 28. This can be a substantial disadvantage inmany applications, such as food, pharmaceutical or agriculturalproducts, where different or additional validity testing may be requiredfor the range of taggant concentrations utilized. Also, many-particlenumbers may have a noticeably different visual effect on the product onwhich the taggant is carried than the effect produced by few-particlenumbers.

A related disadvantage of the two-layer particle system is a difficultyin predicting production quantities. There will be considerabledifferences in production weight and volume of particles needed toformulate different codes. Therefore scheduling individual particleproduction to coordinate with particle demand can be difficult.

On the other hand, if the base of the numbering system is too high, thenumber of particles that must be pre-manufactured to represent a desirednumber of codes becomes impractical.

Overcoming these disadvantages of the two-layer particle system, whilemaintaining a high number of available codes and allowing those codes tobe formulated from a relatively small inventory of differentpre-manufactured particles (i.e. microparticle sets), is the object of afurther aspect of the invention. In this aspect of the invention, themicroparticles have at least three layers, preferably three or four,most preferably three layers. Each of the microparticle sets employed inthe taggant include at least one datum marker layer and at least twovalue marker layers. The datum marker functions to indicate orientationfor the value markers, as already indicated above. However, the datummarker layer or layers is also coded to specify a place in the numbercode so the value markers each designate a value within the indicatedplace. The place code uses colors readily distinguishable from eachother and from those used for value markers so that the orientationindicating datum is not confused with the place value indicating colors.In this way, more numeric information can be coded into a stillmanageable number of microparticle sets so that the total number ofparticles used in any given code may be fixed at a small number, or varyonly over a small number of particle sets required for any given numberand yet the range of available codeable numbers remains high.

At least two numeric places should be selectable by distinguishabledatum marker layer(s) in this system. Desirably the datum markerlayer(s) are selected from at least three, and in some cases suitablyfour or more, available distinguishable marker characteristics and thevalue marker layers are selected from at least four, more preferablyabout 6-10 distinguishable marker characteristics.

Using the same colors as the electrical color-code standard black,brown, red, orange, yellow, green, blue, violet, gray, and white, andincluding the colors gold and silver, a total of 12 distinctive colorindicators are made available. Referring to the color scheme example inTable 1 for assignment of value indicator colors, the additional fourcolors of the 12 color system, i.e. brown, orange, gray and white, canbe employed as datum/place markers.

Because the value indicators have orientation, each pair of valueindicators can have two value assignments. For instance, with brown as aplace indicator and blue and green as value indicators, then blue/greencan be differentiated from green/blue in the respective particlesbrown/blue/green and brown/green/blue. An illustration of thisorientation effect is as shown in Table 3: TABLE 3 gold silver magentablack green yellow blue red total 1 red x x x x x x x — 7 2 blue x x x xx x — x 7 3 yellow x x x x x — x x 7 4 green x x x x — x x x 7 5 black xx x — x x x x 7 6 magenta x x — x x x x x 7 7 silver x — x x x x x x 7 8gold — x x x x x x x 7 56

With such orientation, and an unrestricted number of particles pernumber, 2⁵⁵ codes can be produced in a binary code as described above.However, the number of particles necessary to represent those codes willusually be impractical.

As an alternative to a binary coding system a high-base, low-placesystem can be used. If twelve colors are used with four devoted todatum/place and eight devoted to value, the number of values indicatedby the eight value colors is 56 (twice the 28 indicated by unorientedvalues) and the number of places is 4. Only 224 microparticle sets(56×4) are required to achieve 56⁴ (decimal 9,834,486) different codednumbers, and only four particles are required to express any numberwithin that range. The 224 microparticles can be pre-manufactured asstock inventory.

Optionally null values for any place can continue to be indicated by theabsence of detection of a microparticle of that place, as utilized inthe binary system above, in which case the number of particles utilizedto code an available number will vary from 1 to 4 in the case of afour-place taggant. If greater certainty in detection, or if greaterformulation uniformity is desired, one of the available values at eachplace may be assigned to indicate the zero value for that place. Forinstance, each of the 56 pair sets in Table 3 above, can be assigned oneof the values 0-55. Any number from 0-9,834,485 can then be written withexactly four particles of three layers each, using zero value particlesfor places which are null. In that way, for instance, if sequentialplace value datum indicators are brown, orange, gray and white, zerovalue is red/gold and 55 value is gold/red, the decimal number 55 wouldbe indicated by the four particles

-   -   brown/gold/red;    -   orange/red/gold;    -   gray/red/gold; and    -   white/red/gold.

Unique numbers within the available range can be assigned randomly or inaccordance with any desired protocol. With the four-place system justdiscussed, once the number is assigned, the corresponding taggant can berapidly formulated merely by mixing four (or fewer) members from thestock inventory. In this way, the number of layers remains low and thetotal number of particles required to be manufactured remainsmanageable, while at the same time the variability in the number ofparticles required to be employed in the taggant is reduced oreliminated.

For a given number of available color indicators, and a fixed number oflayers, the balance between colors allocated to place/datum indicatorsand to value indicators will affect the parameters of the number ofavailable codes which can be produced, the number of particles needed todepict the codes and the inventory of particles which must be produced.This is illustrated by Table 4, which shows variations in theseparameters for different allocations for a 12 color, three-layer system,assuming all codes assign a zero value in each place, and assuming thatthe number of particles used in a code is no more than the number ofcolors allocated to places. In Table 4, the columns under the heading“Maximum value per place” indicate the maximum number of codes availablefor each of the indicated places 2-5 when up to 5 of the availableplaces are utilized. TABLE 4 colors total colors allocated colorparticles Row allocated as place pairs to form Maximum Maximum value perplace # to values indicators (values) max. codes codes 2 pl 3 pl 4 pl 5pl 1 11 1 110 110 110 2 10 2 90 180 8100 8100 3 9 3 72 216 373000 5184373000 4 8 4 56 224 9800000 3126 176000 9800000 5 7 5 42 210 1310000001764 74000 3100000 131000000 6 6 6 30 180 729000000 900 27000 81000024000000 7 5 7 20 140 128000000000 400 8000 160000 3200000 8 4 8 12 96430000000 144 17628 21000 249000 9 3 9 6 54 10000000 36 216 1296 7776 102 10 2 20 1024 4 8 16 32

EXAMPLE 1

Using a color set of up to 12 colors as described previously, and withthe aid of Table 4, we can select the number of colors assigned as placeindicators and value indicators to design an optimal numbering systemfor a particular application.

In this example, a series of 3,000 numerically coded particle sets isneeded to tag 3,000 batches of plastic. It is determined that each batchof plastic will need one gram of each of the component particles. It isalso determined that it is important that a fixed number of particles beused to represent the codes so that when a field agent analyzes theplastic they know to look for a specific number of different particles.

From a manufacturing standpoint, it is important to minimize both thenumber of particles needed to represent each code and the number ofdifferent particles needed to be pre-manufactured to represent a desirednumber of codes. For instance, a code that needs two particles torepresent all of the numeric information will require half of themanufactured material as a code that requires four particles, but somenumbers of codes cannot be achieved with a two-particle, three-layersystem or may be obtainable with fewer different pre-manufacturedparticles using a four-particle system. In high volume applications,this difference can be quite substantial, and may be the differencebetween a cost-effective system and one that is not.

To choose an optimal taggant system Table 4 is referenced. It can beseen what combination of place and value indicators will minimize thenumber of individual component particles that will be needed to make upthe desired numeric codes, and what combination will minimize the numberof different particles that will need to be premanufactured in order torepresent the desired numeric codes. Table 4 shows that to obtain atleast 3,000 codes while minimizing the number of particles required torepresent each value, rows 2-4 all achieve more than 3,000 codes withtwo places. In row 2, starting with 12 colors, 10 can be paired as valueindicators, and 2 can be assigned as place indicators. Hence, a base 90number system with 2 numeric places is created having a maximum value of8,100. This is more than sufficient to yield the 3,000 codes required.123 total particles must be manufactured for 3,000 codes. In row 4, with8 colors allocated to values, 3,126 colors are obtained with 2 placecolors. Hence a base 56, with 2 numeric places is adequate to meet theobjective. Only ten total colors are needed and only 109 particles mustbe pre-manufactured.

EXAMPLE 2

A system which uses different datum layers can also be employed to carrydifferent information in a multi-particle taggant, for instance, torepresent different numeric features of a date code.

In this example a tagging system is needed to incorporate expirationdates into a bulk material. Several approaches can be used. First, aJulian date can be implemented, where the number of the day (1-365) isrepresented by one or two particles, and the year is represented byanother particle. This approach would require a two or three particlesystem. If the system is required to span a period of twenty years, atotal of only twenty year-indicator particles are needed. From Table 4it can be seen in Row 7 that 5 value indicator colors are needed tocreate 20 pairs with a single datum color used to indicate the particleas carrying year information. Those 20 pairs can be assigned numericvalues and then used to represent the respective years.

To minimize the number of particles in a given code for day information,the 365 day values can be represented by either one or two particles. Ifone particle is used to represent all 365 days we must select anumbering system that is base 365 or greater. Again, consulting Table 4we see that with three layers and 11 value indicator colors, we do notget a base system greater than 110. See row 1. To accomplish this eithermore colors must be added as value indicators, more than 3 layers mustbe incorporated into the particle, or more than one particle must beused to represent date information.

The other options are to use a four-layer particle or 2 three-layerparticles. By analogy to Table 4, it can be seen that using the colorsavailable, more than 365 different particles can be manufactured using 4layers. Given this approach, 20 year particles plus 365 day-particlesfor a total of 385 particles must be premanufactured to achieve thesenumbers. In actual production however, only one year particle must bemanufactured each year giving a realized annual total of 365 plus 1 fora total of 366 particles per year.

If 2 three-layer particles are chosen to represent the day of the year,we can see from Table 1, row 7 that we can create 400 codes using 5value indicator colors in 2 places, the places being indicated with 2colors different than used to designate the year particle and differentfrom the colors used for values in both the day and year systems. Whenused next to a datum layer, the 5 value indicator colors can be pairedfor a total of 20 value indicators. The 20 particles can bepremanufactured for each of the 2 places yielding a total of 20*2=40particles. Here, the realized annual requirement is 20=12=32 dayindicator particles plus one year indicator particle for a total of 33premanufactured particles. Over the span of 20 years this system willrequire 32 plus 20 particles for a total of 52 particles. This is a muchsimpler system than the four-layer approach discussed above.

An alternate date coding system which could be used is the Month, Day,and Year approach. With this scheme, the highest numeric value needed is31, to represent the number of days in a month. The numbering system canbe arranged into 3 particles with the datum/place layer used todistinguish Month, Day, and Year particles. Consulting Table 1 it can beseen that row 5 will give 42 value indicator pairs using 7 pairedcolors. So, we choose 7 value indicator colors, and 3 place indicatorcolors for a total of 10 colors.

Place 1, which represents the month only needs a total of 12 particles.Place 2 which represents the days of the month will need a total of 31particles. And finally, place 3 will need 20 particles, one for each ofthe years. On an actualized annual basis, 12 plus 31 plus 1 particleswill be need, for a total of 44 particles each year. This issufficiently close to the 33 particles of the previous alternative to bea competitive alternative coding system.

In each of the embodiments of the invention taggants are formulated withmultiple microparticle sets, the collective sets being used to code anindividual number or combinations of numbers. It may be possible thatthe microparticle sets may employ different numbers of layers. Howeverit is preferred that each of the microparticle sets employed in thetaggants of the invention have the same number of layers. In this way,only particles showing the selected number of layers would be taken aspart of the code. Microparticles showing fewer than the selected numberof layers would always be recognizable as incomplete and thereforerejected. If a mixture of microparticle sets of different numbers oflayers is employed, incomplete fragment particles from the higher numberof layers may be mistaken as particle sets of the lesser number oflayers and thus give an incorrect code reading.

Two, three and four layer particles are all easier to manufacture than 5or higher layer particles currently employed in commercial systems.Thus, not only does the invention provide a way of formulating a largenumber of particle codes from a relatively small inventory ofpre-manufactured particles, it also reduces manufacturing costs for theindividual particles. Moreover, for a given layer thickness, fewerlayers provides smaller particles, a desirable objective in manyapplications.

All published documents, including all US patent documents, mentionedanywhere in this application are hereby expressly incorporated herein byreference in their entirety. Any copending patent applications,mentioned anywhere in this application are also hereby expresslyincorporated herein by reference in their entirety.

While the present invention has been described in connection with thepreferred embodiments and with reference to the various figures, it isto be understood that other similar embodiments may be used ormodifications and additions may be made to the embodiments forperforming the same function of the present invention without deviatingtherefrom. Therefore, the present invention should not be limited to anysingle embodiment, but rather should be construed in breadth and scopein accordance with the recitation of the appended claims.

1. A process for identifying bulk particulate matter comprising: a.providing a quantity of the bulk particulate matter which has beenmarked with a coded microparticle taggant material adhesively bound tothe bulk particulate material by a releasable adhesive material andcoded with identifying information; b. activating release of theadhesive material to release the microparticle taggant from the bulkparticulate matter; c. isolating the released taggant from bulkparticulate matter; and d. reading the code from the isolatedmicroparticle taggant.
 2. A process as in claim 1 where the bulkparticle material is seed.
 3. A process as in claim 1 or claim 2 wherethe releasable adhesive material is an organic coating which is solubleor degradable in a solvent.
 4. A process as in any of claims 1-3 wherethe taggant comprises a ferromagnetic material.
 5. A process as in anyof claims 1-4 where the microparticle taggant is characterized in that:the taggant comprises a plurality of microparticles having two or moredistinguishable marker layers corresponding to a predetermined numericalcode, the plurality of particles comprises a plurality of microparticlesets of at least one microparticle, each microparticle set ischaracterized by a specific marker layer combination different from eachother microparticle set, and the combination of microparticle setsemployed in said taggant collectively forms said numerical code.
 6. Aprocess for identifying seed comprising: a. providing a quantity of theseed having a microparticle taggant material adhesively bound thereto bya releasable seed coating material, the taggant being releasable fromthe coating material upon exposure to a solvent, the taggant comprisinga magnetic material and being further characterized in that: the taggantcomprises a plurality of microparticles having two or moredistinguishable marker layers corresponding to a predetermined numericalidentifier code, the plurality of particles comprises a plurality ofmicroparticle sets of at least one microparticle, each microparticle setis characterized by a specific marker layer combination different fromeach other microparticle set, and the combination of microparticle setsemployed in said taggant collectively forms said numerical identifiercode; b. subjecting the seed to a said solvent to release themicroparticle taggant from the seed; c. magnetically isolating thereleased taggant from bulk particulate matter; and d. reading theisolated microparticle taggant.
 7. A process as in claim 6 wherein thesolvent is water or a water wash composition.
 8. A field kit for use inidentifying a bulk particulate material marked with a coded magneticallyattractive microparticle taggant material adhesively bound to the bulkparticulate material by a solvent releasable adhesive material and codedwith identifying information, the kit comprising: a container forholding a sample quantity of the bulk particulate material and a solventfor releasing the adhesive material; a magnet; and an optical enhanceroperable provide an enlarged image of a sample of microparticles.
 9. Afield kit as in claim 8 wherein the container includes a volumetricmarker for identifying a fixed sample quantity of the bulk particulatematerial.
 10. A field kit as in claim 8 or 9 further comprising avolumetric collector for collecting a predetermined sample quantity ofthe bulk particulate material.
 11. A field kit as in any of claims 8-10wherein the magnet is mounted on a stirrer and covered with a removabletaggant collector.
 12. A field kit as in claim 1 lwherein the removabletaggant collector is a white paper.
 13. A field test kit as in claim 8further including a separation means for separating the seed from amixture of the solvent and said taggant produced by contacting said seedwith said solvent.
 14. Bulk agricultural seed having a microparticletaggant material adhesively bound thereto by a seed coating which issoluble or degradable in a liquid solvent to release the taggant. 15.Bulk agricultural seed as in claim 14 wherein the taggant ischaracterized in that: the taggant comprises a plurality ofmicroparticles having two or more distinguishable marker layerscorresponding to a predetermined numerical identifier code, theplurality of particles comprises a plurality of microparticle sets of atleast one microparticle, each microparticle set is characterized by aspecific marker layer combination different from each othermicroparticle set, and the combination of microparticle sets employed insaid taggant collectively forms said numerical identifier code.
 16. Bulkagricultural seed as in claim 14 or 15 wherein the microparticle furthercomprises a magnetic material.
 17. Bulk agricultural seed as in any ofclaims 14-16 wherein the taggant particles are present on the seed in anaverage amount of less than one said microparticle per seed.
 18. Bulkagricultural seed as in any of claims 14-17 wherein said liquid solventis water or a water-based wash composition.
 19. A method of identifyingarticles comprising the steps of: providing a plurality of articles, thearticles having a plurality of mieroparticles adhered thereto by meansof a coating material, the microparticles having a coding associatedtherewith for purposes of identification of the articles; collecting asample of the articles from the plurality; depositing the sample in acollection vessel; washing the sample with a liquid to remove at least aportion of the microparticles adhered to the article sample; collectingthe wash liquid and removed particles in the vessel; removing the washedarticle sample from the vessel; assembling the microparticles washedfrom the article sample; and reading the coding on the microparticlesand correlating the coding to the associated quality corresponding tothe coding.
 20. A method as claimed in claim 19 wherein the samplecollection is deposited in a sieve, inserted into the collection vessel,the sieve retaining the collection during the washing step.
 21. A methodas claimed in claim 19 wherein the microparticles are magneticallyattractive and the assembly of washed microparticles is performed bymeans of magnetic attraction.
 22. A kit for collecting a plurality ofmicroparticles magnetically attractive, the microparticles applied as ataggant to articles, the kit comprising: a collection vessel; a sievefor holding and retaining a quantity of articles having taggantmicroparticles thereon while also permitting microparticles to pass intothe collection vessel during a washing operation; magnetic means at thebase of the collection vessel for assisting in the settling ofmicroparticles within the wash liquid; and a magnetic probe forcollecting microparticles.
 23. A process for marking an article byapplying thereto a taggant, a marking formulation comprising a taggant,or an article marked with a taggant, wherein the taggant comprises aplurality of microparticles having two or more distinguishable markerlayers corresponding to a predetermined numeric code, the plurality ofparticles comprises a plurality of microparticle sets of at least onemicroparticle, each microparticle set is characterized by a specificmarker layer combination different from each other microparticle set,the combination of microparticle sets employed in said taggantcollectively forms said numeric code, the invention characterized inthat: the microparticle sets employed in the taggant include at leastone datum marker layer coded to include place information and at leasttwo value marker layers coded to specify a value within the place, theat least one datum marker layer being readily distinguishable from thevalue marker layers and functioning to identify an orientation of thevalue marker layers.
 24. The invention of claim 23 wherein the at leastone datum marker layer is selected from at least two distinguishablemarker characteristics.
 25. The invention of claim 24 wherein each saidmicroparticle set is made up of three-layer particles composed of onesaid datum marker layer and two value marker layers.
 26. The inventionof claim 25 wherein each distinguishable marker characteristic is avisually distinguishable color or color enhancer or a color, magnetic orradioactive feature distinguishable by a sensing machine.
 27. Theinvention of claim 23 wherein the marker layers each comprises adistinguishably different color or color enhancer.
 28. The invention ofclaim 23 wherein the each said specific marker layer combination has thesame number of layers.
 29. The invention of claim 23 wherein each saidspecific marker layer combination employs three or four layers.
 30. Theinvention of claim 23 wherein each said particle set represents a valueat a given place, the at least one datum marker layer codes for saidplace and the combination of value marker layers codes for said value atsaid place.
 31. The invention of claim 30 wherein the at least one datummarker layer is selected from at least two distinguishable markercharacteristics, the at least two value marker layers are selected fromat least three distinguishable marker characteristics, the total numberof distinguishable marker characteristics is a fixed number and thenumber of marker characteristics allocated as datum markers and as valuemarkers, respectively, is selected to minimize the number of differentmicroparticles necessary to sequentially represent all values within apredetermined range of values with said fixed number of markercharacteristics.
 32. The invention of claim 31 wherein each said markerlayer combination has three layers.
 33. A process for marking an articleby applying thereto a taggant, a marking formulation comprising ataggant, or an article marked with a taggant, wherein the taggantcomprises a microparticle having three or more distinguishable markerlayers corresponding to a predetermined numeric code, said marker layerscomprising at least one datum marker layer coded to include placeinformation and at least two value marker layers coded to specify avalue within the place, the at least one datum marker layer beingreadily distinguishable from the value marker layers and functioning toidentify an orientation of the value marker layers.
 34. The invention ofclaim 33 wherein the combination of value marker layers collectivelydetermines said value within said place.
 35. A process for marking anarticle by applying thereto a taggant, a marking formulation comprisinga taggant, or an article marked with a taggant, wherein the taggantcomprises a microparticle having two distinguishable marker layerscorresponding to a predetermined numeric code, the combination of saidtwo marker layers determining both a numeric place and a value withinsaid place in a binary numbering system.
 36. A process for marking anarticle by applying thereto a taggant, a marking formulation comprisinga taggant, wherein the taggant comprises a microparticle having twodistinguishable marker layers of different color characteristics whereinthe paired combination of color characteristics provided by said twolayers codes for a numeric value.